This section provides background information related to the present disclosure which is not necessarily prior art.
Power supply systems frequently include filters to block common mode noise and differential mode noise. In many cases, these filters are required to satisfy emission and immunity EMC requirements. Common mode noise includes noise on a return path and a supply path in the same direction referenced to a reference voltage (e.g., ground or another suitable reference potential) while differential mode noise includes noise on the return path and the supply path in opposite directions. The filters may include components (e.g., capacitors, differential mode chokes, common mode chokes, etc.) to block the differential mode noise and the common mode noise. For example, the main inductance of a common mode choke may assist in blocking the common mode noise while a stray (i.e., a leakage) inductance of the common mode choke may assist in blocking the differential mode noise.
FIG. 1 illustrates a power supply system according to the prior art. As shown in FIG. 1, the system includes a DC-DC switched mode power supply and an input filter having two inputs (i.e., Input A and Input B) and two outputs (i.e., Output A and Output B). The input of the power supply is coupled to the outputs of the filter. The filter includes X- and Y-capacitors 102a, 102b and common mode chokes 104a, 104b. Each common mode choke 104a, 104b includes windings 106a, 106b, 108a, 108b extending about a magnetic core 110a, 110b. 
As recognized by the present inventors, the power supply system shown in FIG. 1 may experience varying conducted emissions (i.e., common mode noise), resulting in undesirable EMC performance, depending on whether the filter inputs (Input A and Input B) are coupled to separate power sources, to reference voltage(s), and/or to each other. For example, the undesirable EMC performance may be caused by the sum of the DC fluxes of the common mode chokes 104a, 104b not being zero. This in turn may cause common mode chokes 104a, 104b to saturate which then causes a main inductance of the common mode chokes 104a, 104b to decrease.
FIG. 2 illustrates another power supply system according to the prior art. As shown in FIG. 2, the system includes a DC-DC switched mode power supply and an input filter 200 having two inputs (i.e., Input A and Input B) and a single output coupled to the input of the power supply. The filter 200 includes X- and Y-capacitors 202 and common mode chokes 204a, 204b having windings extending about magnetic cores 210a, 210b. 
As recognized by the present inventors, the power supply system shown in FIG. 2 may experience undesirable filtering due to increased distances between the inputs A, B and the X- and Y-capacitors 202. For example, the distances may be increased due components (e.g., fuses, metal oxide varistors (Mov), reverse current protection devices, etc.) coupled between the inputs A, B and the X- and Y-capacitors 202. In some cases, the increased distances (and traces for the components) may cause noise to bypass the X- and Y-capacitors 202 and the common mode chokes 204a, 204b resulting in undesirable filtering.